Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) are semiconductor transistor devices in which a voltage applied to an electrically insulated gate controls flow of current between source and drain. MOSFETs are useful in many power switching applications. In one particular configuration useful in a battery protection circuit module (PCM) two MOSFETs are arranged in a back-to-back configuration with their drains connected together in a floating configuration. FIG. 1A schematically illustrates such a configuration. FIG. 1B shows use of such a device 100 in conjunction with a Battery Protection Circuit Module PCM 102, battery 104, and a load or charger 106. In this example, the gates of the charge and discharge MOSFETs 120 and 130, respectively, are driven independently by a controller integrated circuit (IC) 110. This configuration allows for current control in both directions: charger to battery and battery to load. In normal charge and discharge operation both MOSFETs 120 and 130 are ON (i.e., conducting). During an over-charge or charge over-current condition of the battery 104, the controller IC 110 turns the charge MOSFET 120 off and the discharge MOSFET 130 on. During an over-discharge or discharge over-current condition, the controller IC 110 turns the charge MOSFET 120 on and the discharge MOSFET 130 off.
It is within this context that embodiments of the present invention arise.